Introduction: Protector Disk Light Towers
This pair of lamps uses "protector disks" which are used to protect recordable CDs and DVDs on spindles. A local printing shop had tossed about 50 of them in the trash and the idea for this lamp came about. A ring of 465 nm UV LEDs shines up through the disks, lighting their edges and creating a gradient effect. A cage filament light bulb mounted on top and controlled by a dimmer provides an amber glow that is pleasant to look at without a shade.
A capacitor-based transformerless power supply is used to supply the LEDs. A capacitor in series with the incoming AC power limits the current which is full-wave rectified to feed a string of LEDs. The 10 UV LED string has a total forward voltage of about 32 volts and current of 20 mA, requring a 0.47 uF X2 rated capacitor at 60 Hz/120 V. Nearly every AT/ATX computer power supply in existence has at least one of these capacitors as part of the incoming line filter. A spreadsheet (XLS) is attached which can assist in designing such a transformerless LED power supply running directly from 120/230 volt power (use with caution).
A rotary dimmer switch was disassembled to remove the plastic case and box mounting hardware. Pushing the knob turns the lamp "on", supplying power to the LEDs and activating the dimmer for the top light bulb. Turning the knob brightens the light bulb.
Structurally, there is a wood base and a piece of 1/2" EMT conduit running up through the middle of the protector disks. Spacers made from 3/4" Schedule 40 PVC pipe (painted flat black) maintain the spacing between the protector disks. A low-profile fixture box is placed on top to mount a ceramic light socket. The wires to power the top light socket run down through the center conduit. A hole drilled in the conduit in the base allows to wires to pass through to the dimmer switch.
Everything except the protector disks and the LED subsystem components was purchased at home improvement warehouses and hardware stores.
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